Over 200,000 spinal fixation and spinal fusion procedures are performed annually to correct various congenital and degenerative spinal disorders in humans. Many of these corrective surgical procedures are performed in the lumbar and lumbosacral regions of the spine where traumatic and age-related disc degeneration is common. One such procedure involves the implantation of spinal fixation instrumentation, including plates and rods, using pedicle screws. Another procedure involves the implantation of one or more anterior fusion cages into the intervertebral disc space following a discectomy. These and other known spinal fixation and/or fusion procedures can be quite invasive, traumatic, and time consuming. Further, problems with post-operative stability and pseudoarthrosis are often associated with many of these procedures.
It is well known that the two facet joints, which are formed between each pair of adjacent vertebrae, share and support the axial load on the spine with a respective intervertebral disc. Accordingly, it has been suggested to place screws either directly across the facet joints of adjacent vertebrae or indirectly across the facet joints through the lamina (i.e. translaminar) as both a primary means for spinal fixation and as a secondary means for fixation to augment anterior fusion or pedicle screw fixation instrumentation. Indeed, this suggestion has been accepted by many surgeons as facet screws (direct and translaminar) are now being implanted on a regular basis. In order to further improve upon the use of such facet screws, a minimally invasive method and apparatus for accurately and repeatably placing facet screws across the facet joints and fusing adjacent vertebrae is needed.